Reduced amyloid-A-degrading activity in serum in amyloidosis associated with rheumatoid arthritis.
The ability to degrade amyloid A fibrils was studied in the serum of 31 patients with amyloidosis associated with rheumatoid arthritis, 33 patients with rheumatoid arthritis without amyloidosis, and 47 healthy controls. Fibrillar amyloid A protein and the radial diffusion method were used. The mean degrading activity in serum was significantly lower in patients with rheumatoid arthritis complicated by amyloidosis (58 +/- 19% SD of the activity in a pooled sample of sera from 100 healthy blood donors used as standard) than in patients with rheumatoid arthritis alone (78 +/- 14%; p less than 0.001) or controls (99 +/- 19%; p less than 0.001). Alpha 1-antitrypsin, concentrations of which were raised in both groups of patients, inhibited the degrading activity in serum even in low concentrations. A negative correlation between degrading activity and alpha 1-antitrypsin concentrations was observed. These findings suggest that reduced amyloid-A-degrading activity is due to inhibition rather than to deficiency of enzyme.
D000328:Adult; D000682:Amyloid / Q000097:blood*; D000686:Amyloidosis / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000150:complications; D002097:C-Reactive Protein / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000685:Serum Amyloid A Protein / Q000097:blood* / Q000378:metabolism; D000515:alpha 1-Antitrypsin / Q000378:metabolism
D000682:Amyloid; D000685:Serum Amyloid A Protein; D000515:alpha 1-Antitrypsin; D002097:C-Reactive Protein